Chapter 3 - Polymer blend compatibilization by the addition of block copolymers

Abstract

Since most polymer pairs are inherently thermodynamically incompatible, a wide variety of physical methods has been developed to reduce the interfacial tension in, and thus compatibilize, multicomponent polymer blends. In this chapter, we provide an overview of polymer/polymer phase behavior and elucidate the molecular factors responsible for phase separation. Several strategies introduced to compatibilize phase-separated polymer blends are briefly described, with an emphasis on block copolymers as macromolecular surfactants. The unique attributes of neat block copolymers are examined prior to discussing their ubiquitous use as compatibilizing agents in polymer blends. The criteria and conditions capable of promoting compatibilization are consequently identified, and a molecular-level description of the factors responsible for interfacial modification (and adhesion) is provided. In addition to conventional blends prepared by either high-shear melt/solid mixing or solution casting, we further consider compatibilization of blends with precisely controlled and modified interfaces. One example consists of bilayered polymer films that either contain or are separated by block copolymers differing in concentration and/or molecular composition/weight. Similarly, the effectiveness of adding a premade block copolymer to induce compatibilization in phase-modulated bicomponent fibers is also examined.